We wished to evaluate the effects of smokeless tobacco use during pregnancy. We examined birthweight, preterm delivery, and preeclampsia in women who delivered singleton, liveborn infants in Sweden, 1999-2000. For each snuff user, 10 cigarette smokers and 10 tobacco nonusers were randomly selected. After exclusions, 789 snuff users, 11,242 smokers, and 11,500 nonusers remained. Compared with nonusers, adjusted mean birthweight was reduced in snuff users by 40 grams (95% CI, 7-73 grams) and in smokers by 206 grams (95% CI, 194-218 grams). Preterm delivery was incrreased in snuff users and smokers (adjusted odds ratios 1.98, 95% CI, 1.46-2.68 and 1.57, 95% CI, 1.38-1.80, respectively). Preeclampsia was reduced in smokers (adjusted odds ratio 0.63, 95% CI 0.53-0.74), but increased in snuff users (adjusted odds ratio 1.58, 95% CI, 1.09-2.27). Snuff use increased risks of preterm delivery and preeclampsia. Snuff is not a safe alternative to cigarettes in pregnancy.